This invention relates to a printer which will be called an X-Y plotter hereinafter.
A conventional X-Y plotter disclosed by J. O. Yeiser in U.S. Pat. No. 3,761,950 prints or gives a mark, such as a letter, a symbol, a sign, or a figure, on a recording sheet by at least one writing element, such as a pen and the like. More particularly, the plotter comprises a pen carriage for carrying the pen in a first predetermined direction, namely, an X-direction, and a sheet feeder for feeding the recording sheet in a second predetermined direction, namely, a Y-direction orthogonal to the X-direction. The sheet feeder is displaced from the pen carriage in the Y-direction. A flat platen plate which is referred to as a machine table is fixedly laid under the pen and extended towards the sheet feeder. The pen and the recording sheet can be moved in the first and the second directions, respectively.
Before recording, the recording sheet is extended from the sheet feeder on the flat platen so as to place the recording sheet under the writing element. The pen is brought into contact with the recording sheet each time when a mark is recorded on the recording sheet by the pen. Since the pen carriage is displaced from the sheet feeder in the Y-direction, as mentioned before, the pen is widely movable along the first predetermined direction without being brought into contact with the sheet feeder. In other words, it is possible to effectively utilize the recording sheet along the X-direction. However, frictional force between the recording sheet and the platen plate is very large when the recording sheet is urged to the platen plate by the writing element. The frictional force prevents the recording sheet from being favorably and smoothly fed in the Y-direction. As a result, this plotter is incapable of giving each mark at a high precision on the recording sheet.